
<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style type="text/css">
        * {
            margin: 0;
            padding: 0;
        }

        ul {
            list-style: none;
        }

        .wrap {
            width: 330px;
            height: 30px;
            margin: 100px auto 0;
            padding-left: 10px;
            background-image: url(imgs/bg.jpg);
        }

        .wrap li{
            background-image: url(imgs/libg.jpg);
        }

        .wrap > ul > li {
            float: left;
            margin-right: 10px;
            position: relative;
        }

        .wrap a{
            display: block;
            height: 30px;
            width: 100px;
            text-decoration: none;
            color: #000;
            line-height: 30px;
            text-align: center;
        }

        .wrap li ul {
            position: absolute;
            top: 30px;
            display: none;
        }

    </style>

    <script src="jquery-3.2.1.min.js"></script>
</head>
<body>
<div class="wrap">
    <ul>
        <li>
            <a href="javascript:void(0);">一级菜单1</a>
            <ul>
                <li><a href="javascript:void(0);">二级菜单1</a></li>
                <li><a href="javascript:void(0);">二级菜单2</a></li>
                <li><a href="javascript:void(0);">二级菜单3</a></li>
            </ul>
        </li>
        <li>
            <a href="javascript:void(0);">一级菜单1</a>
            <ul>
                <li><a href="javascript:void(0);">二级菜单1</a></li>
                <li><a href="javascript:void(0);">二级菜单2</a></li>
                <li><a href="javascript:void(0);">二级菜单3</a></li>
            </ul>
        </li>
        <li>
            <a href="javascript:void(0);">一级菜单1</a>
            <ul>
                <li><a href="javascript:void(0);">二级菜单1</a></li>
                <li><a href="javascript:void(0);">二级菜单2</a></li>
                <li><a href="javascript:void(0);">二级菜单3</a></li>
            </ul>
        </li>
    </ul>
</div>
</body>
</html>
<script>
//    $(function(){
//        $(".wrap").children("ul").children("li").mouseenter(function(){
//            $(this).children("ul").show()
//        });
//        $(".wrap").children("ul").children("li").mouseleave(function(){
//            $(this).children("ul").hide()
//        });
//    })
    $(function(){
        $(".wrap>ul>li").mouseenter(function(){
            //$(this).children("ul").show().parent().siblings().children("ul").hide()
            $(this).children("ul").show()
        });
        $(".wrap>ul>li").mouseleave(function(){
            $(this).find("ul").hide()
        })
    })
    
    
    
</script>